Lesson 5: Sun Calendar and Crop Planting - Student Worksheet

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Background information:

As you have discovered from the previous activities, the amount of sunlight affects the temperature. During our winter months, the northern hemisphere receives fewer hours of sunlight. Temperature both of the air and the soil and the hours of light affect plants that we grow. If we are to be successful farmers we must discover the proper time to plant each type of crop. In ancient times, many cultures made elaborate astronomical tools in order to determine the exact day to plant. For example, in MesoAmerica, the Mayan people in the Yucatan, the Aztec people and their Toltec forebears in Mexico City, and the Zapotec people of Oaxaca built observatories. On particular days of the year, certain stars and the sun would shine through openings in the buildings. These dates would mark such events as the solar solstice (when the northern hemisphere is most directly tilted toward the sun and our daylight hours are the longest). Native Americans of the Plains built rings of stone that aligned to the sun during solar equinox. European Americans mistakenly called these circles "medicine wheels." Other examples of the astronomical tools built by our ancestors include Stonehenge, England with its arranged series of large rocks and Chaco Canyon in the American Southwest with its petroglyphs.

All of these ancient tools function because the earth is tilted and revolves around the sun. This means that when viewed from the earth, the sun will appear to have a slightly different path each day. The MesoAmericans would construct buildings with long window shafts. The angle of the window would allow only the light of a certain star or the sun when the earth was in the exact position. At a certain time each year the light would be able to travel down the shaft. If a mirror was placed at the end of the shaft, it would reflect the light on a specific spot. To demonstrate how the MesoAmerican observatories worked, take a long tube, box, and a mirror. The tube functions as the long shafts built into the ancient observatories. Set up the box, tube and mirror on the ground so that the tube sticks out of a sun-facing window. Tape a piece of paper to the wall so that the light spot hits it. What happens to the light spot after a few minutes?

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If the sun was in a slightly different position, would the tube be in the correct position to shine on the mirror?

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Since the sun rises and sets in a different location each day, the MesoAmericans built their observatory window shafts to allow the sun in only on a certain day. We can observe the sun's movement each day with the following activity.

Tape clear plastic sheets on the eastern facing window. Trace the horizon with an overhead projector pen. Removing the sheets, recopy the horizon on regular paper. Each week mark the location of the sun at sunrise.

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Hypothesis/Research:

In the next activity you will be growing radishes, cilantro, corn, and beans. Research these crops to determine the best growing techniques and seasons. This is usually listed on the back of the seed packets. When you have completed your map of the sun's movement on the horizon, mark on your map the location of the sun during the best planting time for each of the four crops.

Radishes:

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Cilantro:

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Corn:

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Beans:

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